The characterization of Cetiosaurus is based on the Middle Jurassic English species C.oxoniensis known from most parts of the skeleton except the skull. No part of the skull is known except perhaps for a single incomplete tooth of the spatulate variety. 

The heart-shaped teeth of Cardidon have often been referred to Cetiosaurus, but this cannot be established. The numbers of cervical and dorsal vertebrae are unknown. The sacrum is not known. The arches and spines of the proximal and middle caudals resemble those of Camarasaurus. 

Cetiosaurus was the first sauropod to be discovered. When is was named in 1841, it was the largest known land animal. "Whale lizard" belonged to a primitive family called Cetiosauridae. 

Cetiosaurus had a moderately long neck, a capacious body and a relatively short tail. The humerus (forearm bone) may have been the same length as the tibia (shin bone) not shorter, as in most sauropods. Length 18 m (59 ft) Weight 27 tonnes.